stunted growth, congestive heart failure due to anatomic abnormalities of the heart, sarcomas and other tumors, etc... unfortunately most do not manifest itself until after the eastern is older. the only visual sign we as hobbyist can use is split/aberrant scales to judge the amount of inbreeding. if you've seen enough of them (and there's plenty of inbred easterns floating around for everyone to look at, split scales due to inbreeding are very distinct looking.